Inorganic Chemistry
Article
stirred under N2 gas in an oil bath at 130 °C for 72 h. Then, the
solvent was evaporated from the reaction mixture under vacuum, and
the obtained solid residue was washed with water to remove an
inorganic salt. The solid was treated with chloroform (50 mL, three
times) to extract a crude product, followed by drying the extract with
magnesium sulfate. Then, the solvent was evaporated under vacuum.
Finally, the obtained residue was boiled in tetrahydrofuran for 2 h and
filtered off to separate the filtrate containing impurities. The obtained
solid was isolated and dried to provide 1,3,6,8-tetrakis(4-
(methoxycarbonyl)phenyl)pyrene (0.61 g, 84% yield).
of TC (D, %) was obtained from eq 1, where C0 and A0 are the initial
concentration and the absorbance of TC, while Ct and At refer to the
respective parameters at a certain time (t).
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At Ñ
Ct Ñ
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D = 1 −
× 100 = 1 −
× 100
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A0
C0
(1)
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For better comparison between photocatalytic, sonocatalytic, and
sonophotocatalytic processes, the TC degradation using each of these
three methods was separately investigated. Ultrasound waves were
applied either in the absence (sonocatalytic process) or in the
presence of irradiation by a 300 W halogen lamp (sonophotocatalytic
process) by placing an ultrasound high-intensity probe (20 kHz
frequency, 200 W power) into the reaction suspension. In recycling
tests, the utilized catalyst was isolated, washed with distilled water,
and dried at 60 °C prior to reuse in subsequent runs.
In the next stage, a solution of NaOH (37.5 mmol, 1.5 g) in 75 mL
of H2O/THF (1:1) was introduced into a 200 mL round bottom flask
containing 1,3,6,8-tetrakis(4-(methoxycarbonyl)phenyl)pyrene (0.78
mmol, 0.58 g), and the resultant suspension was stirred overnight
under reflux. Then, solvents were evaporated under vacuum, and
water was added to the residue, resulting in a transparent yellow
solution. This was stirred at 25 °C for 3 h, and its pH value was set to
1.0 using concentrated HCl. Filtration was used to collect the
resulting yellow solid that was abundantly washed with water several
times. The crude product was recrystallized from DMF and filtered
off. Furthermore, the product was washed with chloroform and dried
under vacuum, resulting in H4TBAPy (0.51 g, 92%) (Scheme 1).
2.3. Preparation of [Zr6(μ3-OH)4(μ3-O)4(OH)4(H2O)4(μ8-
TBAPy)2] (NU-1000). NU-1000 was synthesized in compliance
with a reported process.59 In brief, benzoic acid (22 mmol, 2.70 g)
and ZrCl4 (0.30 mmol, 70 mg) were combined in DMF (10 mL) and
then dissolved using an ultrasonic treatment. In the next stage, the
obtained transparent solution was incubated in an oven at 80 °C for 1
h and cooled down to room temperature. To this solution, H4TBAPy
was added (0.06 mmol, 40 mg), followed by sonication for 20 min.
The obtained yellow suspension was heated in an oven at 120 °C for
48 h and then cooled down to room temperature. The resulting
suspension was filtered off, producing a yellow polycrystalline solid
(35 mg after activation; 54% yield). Then, it was washed with DMF
and consequently activated with HCl as shown by Feng et al.60
2.4. Preparation of Hybrid NU@ZIS Nanocomposites. In this
stage, a single-step solvothermal procedure was used to obtain hybrid
NU@ZIS composites (ZIS = ZnIn2S4). In brief, specific content of
the as-prepared NU-1000 powder (e.g., 2.75 g for NU@ZIS20) was
mixed with glycerol (5.0 mL) and DMF (15.0 mL) under
ultrasonication. Then, In(NO3)3·XH2O (0.586 g), TAA (0.301 g),
and ZnCl2 (0.136 g) were added to the mixture which was shaken at
25 °C for 90 min. The obtained suspension was transferred to an
autoclave (150 mL, stainless steel lined with Teflon) that was sealed
and heated at 160 °C for 10 h. After cooling to ∼25 °C, the autoclave
was opened and the solid product was abundantly washed with EtOH
and distilled H2O several times and then dried at 60 °C. The obtained
NU@ZIS samples included the materials with 5, 10, 20, and 30 wt %
ZIS, which were labeled as NU@ZIS5, NU@ZIS10, NU@ZIS20, and
NU@ZIS30, respectively. For comparative purposes, ZIS was also
synthesized using a similar solvothermal procedure in the absence of
NU-1000.
2.5. Photocatalytic, Sonocatalytic, and Sonophotocatalytic
Experiments. To evaluate the photocatalytic activity of the hybrid
NU@ZIS nanocomposites in the visible-light-induced decomposition
of TC in an aqueous solution, a 300 W halogen lamp with a UV filter
was selected. In each test, aqueous TC solution (20 ppm, 300 mL)
was added to a 500 mL beaker. The solution was set to an optimal pH
of 9.0 by adding NaOH (1 M, 12 mL), followed by addition of the
catalyst (0.2 g·L−1). Initially, to attain equilibrium (adsorption−
desorption) between TC and the catalyst, the obtained suspension
was subjected to vigorous magnetic stirring in darkness for 20 min. A
cold water circulator was used to maintain a constant reaction
temperature during the degradation process. As the light was turned
on, aliquots (1.5 mL) were carefully taken out from the reaction
solution at regular time intervals with a syringe. Prior to analysis, the
suspension was filtered using syringe filter discs (0.45 μm,
polytetrafluoroethylene). Then, the absorbance of each sample was
measured at 350 nm on a UV−vis spectrophotometer to investigate a
decrease in TC concentration at different times. The degradation rate
2.6. Experiments with Radical Scavengers. A scavenger (i.e.,
IPA, isopropanol; EDTA, ethylenediaminetetraacetic acid; or BQ, 4-
benzoquinone) was added into TC solutions for probing the presence
of •OH (hydroxyl radicals), h+ (positive holes), and •O2− (superoxide
radicals), respectively. The following starting loadings of IPA (1
mmol), EDTA (1 mmol), and BQ (0.1 mmol) were used.
2.7. Cell Culture. Skin fibroblast cells (Hu02) were used to
perform the cellular experiments. Hu02 cells for MTT assays were
acquired from the National Cell Bank of Iran (NCBI). The cell
cultures were grown and kept under 6% (v/v) carbon dioxide
atmosphere in tissue culture flasks (T80 cm2, Falcon) consisting of
DMEM/L-glutamine, 7% (v/v) FBS, and 1.5% (v/v) penicillin/
streptomycin at 37 °C.
2.8. Cytotoxicity Examination. According to Mosmann’s
study,61 MTT assays were used to evaluate the Hu02 viability. This
relies on a color change of yellow tetrazolium salt (soluble in H2O) to
purple formazan (insoluble in H2O). Due to a decreased quantity of
live mitochondrial cells, an amount of the formed formazan directly
correlates with the number of live cells.62 96-well plates were used to
seed the cells and incubation was performed at 37 °C. Then, the NU-
1000, ZIS, and NU@ZIS suspensions in PBS at 1 mg/mL
concentration were sonicated for 2 h using an ultrasonic bath. The
obtained samples were diluted with a growth medium and then
poured into the seeded wells for yielding different concentrations
(500, 400, 300, 200, 100, 50, and 0 μg·mL−1). Following incubation at
37 °C for 24 and 72 h, the medium used for growth was taken out
from all of the wells and substituted by a fresh medium (100 μL) and
a solution of MTT (10 μL; 0.5 mg per 1 mL of PBS). In the next
stage, incubation of the well plates was done for 4 h until a purple-
colored formazan product was produced. Then, 90 μL of the test
solution was taken out and 100 μL of DMSO was poured into the
wells for dissolving the formazan crystals. The well plates were
incubated at 37 °C for 15 min, followed by centrifugation for 3 min at
1200 rpm. In addition, the supernatant (100 μL) was transferred into
a new well (96-well plate) and absorbance was determined at 530 nm
with the use of a microplate reader (BioTek ELx808). Then, the cell
survival was obtained as a relative percentage by comparing the
absorbance in treated wells and control wells. Finally, the MTT
experiments were repeated three times for all composite nanomateri-
als and the average values were used in this work.
2.9. Aquatic Toxicity. Aquatic toxicity of the reaction solutions
against E. coli was assayed prior to and following the sonophotoca-
talytic degradation of TC. In the first method,63 Petri dishes were
prepared by mixing adequate volumes of agar and nutrient broth.
Then, the obtained mixture was boiled resulting in the formation of a
gel within not less than 1 h. E. coli (50 μL; stock solution with ∼1 ×
108 CFU/mL) was spread on the agar surface. A control experiment
was assembled with the agar formed using water from sonophoto-
catalytic experiments (performed during 4 h) for ensuring that the
antibacterial test result is caused by an antibiotic degradation instead
of potential catalyst leaching or change in H2O chemistry. In addition,
we utilized the aqueous solutions obtained after sonophotocatalytic
procedures (at 0, 15, and 30 min of the reaction time) to prepare agar
and evaluate the level of changes in the bacterial growth. E. coli growth
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Inorg. Chem. 2021, 60, 9660−9672
Abazari, Reza
